Which of the following is true about soluble phosphorus?

The statement that soluble phosphorus is essential for plant nutrition is accurate. Phosphorus plays a crucial role in various plant processes, including energy transfer, photosynthesis, and the synthesis of nucleic acids, which are vital for plant growth and reproductive development. For plants, phosphorus is typically absorbed in its soluble forms, primarily as phosphate ions. Thus, the availability of soluble phosphorus directly impacts plant development and overall health.

The other points presented in the question do not accurately represent the nature of soluble phosphorus. Soluble phosphorus is indeed available for plant uptake, contrary to the first statement. It is not the only form present in soil, as phosphorus can exist in various forms, both soluble and insoluble, subject to soil conditions and chemistry. Moreover, while phosphorus may exist in both precipitated and organic forms, soluble phosphorus specifically refers to its more available form rather than these other forms. This makes the option asserting its essential role in plant nutrition the most accurate.